Electric-arc welding



' A. CHURCHW'ARD. v

4 ELECTRIC ARC WELDING.

APPLICATION FILED FEB. 18, 1920.

1,416,449., Patented May 16, 1922.

entree stares ALEXANDER- oiruncnwnzen, or NEW YORK,

m an -came- METALS COMPANY, INC., A CORPORATION YORK.

unaware- RC WELDING.

Specification of Letters Patent.

Patented May is, 192.2.

Application filed- February-18, 1920. Serial-No. 859,495,

T all whom it may concern:

Be it known that I, ALEXANDER Cannon- WARD, a citizen of the United States, residing at New York city, county of New York,

specification.

My invention relates to electric arc'welding and particularly to .a welding system of the' constant-current type, where the variations in the arc current are compensated by a pressure variable carbon-pile controlled by a solenoid. One object of my invention is to provide an improvement in the automatic current controlling means of such a system..

Another object is to provide means for shunting the current from the carbon-pile to a protective resistance in parallel therewith whenever the arc is short-circuited. By means of this protective resistance, the overheating and burning out of the carbon-pile is-positively prevented and I thereby produce acompensator which will bev practically fool-proof tremely' durable and having a greatly increased life.

Further objects will appear from the following description taken in connection with the accompanying drawing wherein several embodiments of myinvention are illustrated.

Figure 1 is a'diagrammatic view of acorniplete welding circuit including a generator,- welding electrodes, and a variable resistance operated by a solenoid.

.- Figure 2 is a diagrammatic view of a pressure variable carbon-pile with one form of my protective'resistance applied thereto. Figure 3 is a diagrammatic view of a carbonile similar to that in Figure 2 showing asecond form of protecting resistance applied thereto. a

Figure 4 is a view similar to Figures 2 and 3 but showing a third form of protective resistance.

While welding with amachine of the constant current system above described, it is customary to operate with a comparatively low I. R. drop through the variable resistance (from 1416 volts). When the arc is short-c'ircuited, however, the drop through the variable resistance increases greatly, often becoming as high as 31 volts, and the current thereby produces an excessive heating eflect therein.

and, consequently, eX-

Ordinarily the arc is short-circ-uited only for an instant before drawing the arc and in such a short interval the variable resistance has no time to overheat. It has-been found, however, that in practice,

despite all precautions, the arc will often be short-circuited for longer periods of time either through accident or through heed lessness in operating Careless workers gwill sometimes allow the electrode to remain lying upon the work for considerable periods of to overheat and burn up rapidly. v

In order to reduce the cost of renewals and avoid the danger of fire resulting from accidents or from careless-operations,-I have concelved the idea of constructing a fool-. proof appara't-us by utilizing a safety protective resistance in shunt with the compensating resistance adapted to absorb the largerportion of the current Whenever the arc is short-circuited.

N. Y., ASSIGNOR T'O WILSON WELDER &

time, thereby causing the variable resistance I have shown my protective means applied to a carbon-pile compensating resistance, and have illustrated three distinct forms thereof (see Figures In each of the illustrated forms the carbon pile is composed of a series of. resistor elements 2 arranged face to face in imperfect contact. As shown in Figure 1 the current is supplied in each instance by amotor generator 3 and may be 7 traced as follows: from the generator '3 through the wire 4, the carbon-pile 1, the wire 5, the controlling solenoid 6, the, wire '7,v the welding electrode 8, the work 9 and from the wire 10 back to the generator 3. The compressing lever 11 is pivoted at 12 and is actuated by the difference inpull of the spring 13 and the plunger 14 operated by the controlling solenoid 6. The dash-pot 15 serves to dampen somewhat the vibrations of the compressing lever 11.

The first form of my carbon-pile protec- 'tive means is shown in Figure 2 and comprises the coil of resistance wire 16 preferably of Fnichrome metal, connected-to each one of the resistor elements 2. i

In the form of pile protective means shown in Figure 3, I have shown a coil of resistance wire 16* similar to the resistance shown in Figure 2. Instead of being connected to each of the resistor elements. 2, as in Figure 2, it is connected only to the end elements and to the intermediate elements 17 and 18.

In Figure. 4 I have shown a third form of pile protective meanscomprising three parallel coils of resistance wires 19,20 and 21 adapted to be connected by the switch 22. As will, be'evident, this construction allows the effective value' of the protective resistance to be varied. at will. This may be I illustrated by an example. In one construe that the protecting tion the coils 19, 20 and 21 were made of equal resistances, each onebeing capableof absorbing7 5 amperes. In operating this de-- vice, when the coil 19 only was employed, the protective resistance absorbed 75 amperes. When the coils 19 and 20 were both connected to the terminals of the carbonpile 1, the protective resistance was able to carry 125 am'peres. Similarly, 'when allthree coils 19, 20 and 21 wereconnected in parallel to the terminals of the pile, their combined capacity was 17 5 amperes.

While I have described my invention in connection with a carbon-pile, it is obvious resistancemay be utilized on'othe'r modified forms of variable resistance compensators. I

- In.,each form of my invention the app-aratus is so designed that the value of the vaf riable resistance is normally much less than the value of the constant protective resistance. \Vhenthe arc becomes short-circnited, however, the variable resistance will auto- 'matically increase and become greater than the protective resistance.

In operation, when the are is drawn, substantially all of the current will flow through the variable resistance, but when the electrode is in I. contact with the plate, or

' the arc is otherwise short-circuited, substantially all of the current will flow throu h the protective resistance. Consequently, t e

variable compensating resistance will be absolutely prevented from accidental overheating or burning. out. As has been indicated above, the protective resistance renders the apparatus practically fool proof and thereby I am enabledto'savethe cost of frequ nt renewals; v v

I desire it to be understood that the three embodiments herein 7 disclosed are given only by way-0f illustration, and not of limitation, and that my invention may be practiced in many other ways withinthe scope of thefollowing claims.

I claim 1. An electric arc welding apparatus comprising, a pressure variable compensating resistance comprising a plurality of carbon resistor elements, a bridging resistance electrically connecting two of said resistor elements, the resistance between the twocarbon resistor elements being normally less than said bridging resistance.

2. Ina system of electric arc welding, a

welding circuit including a source of potential, a pressure variable resistance comprising a plurality of resistor elements adapted to contact with one another, a resistance in shunt with a plurality of said elements, and

means for rendering said resistance normally. ineitective and for causin said resistance to absorb the larger portion of the current whenever the arc is short-circuited.

3,'In a system of electric arc welding of the constant-currenttype, a'welding circuit including a source of potential, welding elec the value of the constant resistance lying be-- tween the maximum and minimum values of the variable resistance.

5. In an electric arc welding system, a

pressure variable resistance pile responsive to the fluctuations of the arc current, and an" adjustable protecting resistance arranged across theterminals of the pile adapted to automatically absorb substantially all of the current when the arc is short-circuited. 6. In a constant-current electric .arc welding systema compensating resistance responsive to fluctuations in the welding our rent, .and a protecting resistance normally" substantially ineflective for absorbing substantially all of the current whenever the arc is short-circuited, whereby the compensating resistance is-prevented from overheating or burning out. 4

7. An arc welding apparatus comprising a compression rheostathaving a pile of resistor elements arranged face-to face'in con- ,tact with one another and having an adj ustable safety protecting resistance connect ed to the terminal elements of the pile said protecting resistance comprising a plurality of resistances in parallel, and means for successively connecting them.

ing system, a compensatin \resistancererent, and a protective resistance of nichrome wire bridgin the terminals of said com-' pensating resistance for absorbing the larger portion of the current whenever the arc is short-circuited, said protecting resistance 81 In aconstant-current electric arc weldsponsive to fluctuations in t e welding c'urcomprising a plurality of parallel branches,

and a switch adapted to introduce any desired-number of branches into thecircuit.

In testimony whereof, I have affixed my signature to'this specification.

' ALEXANDER QHURGHWARD. 

